1. Field of the Invention
The present invention relates to a void-free circuit board and a semiconductor package having the same. More particularly, a void-free circuit board capable of preventing voids with air captured therein due to non-uniform capillary action resulting from an uneven gap formed between a semiconductor chip and a substrate during a process of injecting underfill material into the gap, thereby preventing a defective product and improving product reliability, and a semiconductor package having the same.
2. Description of the Related Art
Recent trend of compact and miniaturized electronic devices has required high-speed, high-function and high-density mounting methods in the packaging technology of semiconductors. In response to such a demand, flip-chip mounting technology in a chip-scale package has been developed.
The generally known flip-chip mounting technology involves techniques of mounting an unpackaged semiconductor chip on a circuit board to assemble into a semiconductor chip package.
FIG. 1 is a sectional view illustrating a conventional semiconductor package. As shown, electrode patterns 3 are formed as a signal line on an upper surface of a circuit board 2, and solder-resist protective layers 4 are formed in a predetermined thickness above the circuit board 2.
The protective layer 4 is not formed on an immediate vicinity of a connection terminal 3a (see FIG. 2) of the electrode pattern 3, thereby forming an opening 6 exposing the connection terminal 3a of the electrode pattern 3 and an upper surface of the circuit board 2 around the connection terminal 3a. 
Solder balls 7 are placed on the connecting terminal 3a of the electrode pattern 3 in a corresponding position to electrode terminals (not shown) formed on the undersurface of a semiconductor chip 1. The semiconductor chip 1 is electrically connected to the circuit board 2 via the solder balls 7.
Mounting the semiconductor chip 1 onto the circuit board 2 as described above forms a gap between the semiconductor chip 1 and the circuit board 2 due to the height of the solder balls 7 attached to the undersurface of the semiconductor chip 1. As a result, the power of supporting the semiconductor chip 1 is weakened and portions in contact with the solder balls 7 may be damaged due to stress from vibration.
Therefore, underfill material made of insulation resin is injected by a dispenser (not shown) between the semiconductor chip 1 and the circuit board 2, and cured to form an underfill part 8 supporting the semiconductor chip 1, thereby completing a flip-chip semiconductor package 10.
However, as shown in FIG. 2(a), as the underfill material is injected in an opposite or different direction from the electrode pattern 3 to form the underfill part 8, the gap between the semiconductor chip 1 and the circuit board 2 is not uniform, resulting in a void in which air fills up the opening 6, as shown in FIG. 2(b).
That is, a gap T1 between the semiconductor chip 1 and the circuit board 2 in the opening 6 is larger than a gap T2 between the protective layer 4 exposed in the opening 6 and the semiconductor chip 1, and thus, capillary action is less effective in the gap T1 during the injection of the underfill material. Consequently, the flow rate of the underfill material moving through the gap T1 is relatively slower than that through the narrower gap T2.
In this case, as shown in FIG. 2(a), the underfill material injected in a direction B between the semiconductor chip 1 and the circuit board 2 flows along a direction C traced in a dotted line, at a slower flow rate in the gap T1 than in the gap T2 to fill up the space between the opening 6 and the semiconductor chip 1. As a result, the underfill material reaching an outer surface of the solder ball 7 captures air to form the void V.
The void V formed in the underfill part 8 is inflated and exploded in a process of heating the underfill part 8 at a high temperature of at least 200 degrees Celcius during a reliability test, quality test or manufacturing process, which has been a major factor for producing a defective product, degrading product reliability.